Case study of longwave contribution to dust radiative effects over East Asia

In order to evaluate the impacts of LW contribution to aerosol radiative effects over East Asia, a dust longwave radiative parameterization scheme is integrated into the online mesoscale dust forecasting model GRAPES_CUACE/dust. A case modeling study shows that about half at surface and one third at TOA of the dust negative shortwave radiative forcing are cancelled by its positive longwave forcing over the dust affected area. In the dust layer, longwave radiation emitting by dust cools the atmosphere, which counteracts about 17% of shortwave heating of atmosphere during daytime and results in cooling of atmosphere simply during nighttime. At the same time, the atmosphere beyond the dust layer is warmed because of absorbing the LW radiation emitted by dust layer. Dust longwave contribution exerts more evident impact on the air temperature in lower atmosphere and surface. The surface air temperature cooling rate resulting from the dust solar radiation is cancelled about 40% by dust longwave warming at daytime. At nighttime, dust longwave contribution warms land and sea surface. The online calculation of dust LW radiation reduces about 15% relative errors of predicted AOD based on the dust model with only SW radiative feedback. This case study result suggests that dust longwave contribution has important impacts on the earth-atmosphere energy process, especially on the surface and in the lower atmosphere and should not be neglected in the study of dust radiation effects.